[vsnet-chat 5973] Re: [AAVSO-DIS] Eta Gem Request & other LP EBs

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Re: [AAVSO-DIS] Eta Gem Request & other LP EBs

> There are a few shallow depth, long-period EBs that come due in the next
> year or so.  It would be nice if a better ephereris for all these stars was
> available. Besides eta Gem, I show the following stars eclipsing based on
> periods and dates from Burnham's Celestial Handbook.
> 
>     32 Cyg (per = 1148d) mid-eclipse April 1, 2003
>     31 Cyg (per = 3802.84d) mid-eclipse Sept 3, 2003
>     zeta Aur (per = 972.176d) begins Nov 13, 2003, ends Dec 18, 2003
> 
> All these eclipses last a long while - weeks or months around their mid
> dates, so good monitoring needs to happen well beforehand.  The visual dips
> are also very small - only a few 10th of a mag in 'v'.  They are thus for
> CCD guys, best in redder bands.

   They are all zeta Aur-type ecliping binaries.  In these systems, a hot
star (usually main-sequence B star) is eclipsed by a (super)giant (usually
K star).  So the depths of eclipses are larger in short wavelengths.
The depths are much more striking in the B band (good targets for B-filtered
human eyes?, although I don't recommend to use a U filter...) rather than
in red CCD bands.

Regards,
Taichi Kato

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